Electric glow-lamp



UNITED STATES PATENT OFFICE.

HEINRICH BA'UMHAUER, Ul CIIARLOT'IENBU'RG, NEAR BERLIN, GERMANY, A BY MESNE ASSIGNMENTS; T0 IPATENT-TRE'UELANID-GlESELLSCHAFT F'U'LE HSIGNOR, R ELEO TRISGHEfGLUHLAMPEN, M. B. IL, 013 BERLIN, GERMANY, A CQRPORATION OF -GERMAJIY,

v r ELECTRIC GLOW LAMI.

1 401 510. Specificationof Letters Patent. No Drawing.

To all to 710m it may concern;

Be it known that I, I'IEINRIGH Baueri-mnnm'a German citizen, and resident of Cl'iarlottenburg, near Berlin, Germany, have invented certain new and useful Improvements in Electric Glow-Lamps, of which the following is a specification.

My invention relates to electric glow lamps and more especially to carbon filament lamps, and its particular object is a glow lamp of this type having a longer life and a higher load capacity than the carbon filament lamps heretofore devised.

According. to my invention the lamp 'is fill-ed with rare gases such as argon, neon, helium, crypton, xenon in a state of high purity.

It is well known that the life of a carbon filament can be increased considerably by filling; the lamp with a suitable gas such as for instance nitrogen or carbonic acid. Pro vided that the gas pressure was kept sufficiently high a considerable diminution of the vaporization of carbon and a correspond ingly longer life of the filament is obtained, the nitrogen. or other gas used being practically inert. On the other hand by sacrificing the longer life it was possible, in lamps of that kind, to place the filament under an increased. load and to thus obtain a superior economy.

If nitrogen and the like were replaced by one of the rare gases mentioned itllOVB, no particular difference could at first be ascertained with regard to the carbon filament. In both cases a limit was soon reached where the vaporization of the carbon and the de struction of the llilament could not be pre vented any more by the gases placed under reasonable pressure. It is true that the so called concentrated disposition of the lilament in an atmosphere of rare gases furnish very remarkable results in another direction. Thus formstance the lite of a vlamp consumingabout-- .one and a halt Watt per candle can be broughtup to several hundred hours and the length of the filament can be kept so low as to impart to it very useful mechanical properties. This vas more than could be expected from the carbon filament as such, but it seemed at the same tune that there were no means for exceeding the inn- Application filed November 13, 1917. Serial No. 201,880.

Patented Dec. 2'3, 1921.

its put to the carbon by its nature, its vapor tension and its inherent disintepration.

ltis lurther known that as? rare gases employed for filling tho lamps were always mixed with small quantities of nitrogen and other substances,and there were no methods known 'lor totally getting rid of these admixtures. Moreover, so far as I am aware, the art up 'toldate has not recognized that these remaining nitrogen admixtures would have any detrimental effect upon the function of the lamp.

In the meantime methods have been found for obtaining commercial quantities of the the rare gases, and quite especially argon, n a state of almost perfect purity. My in vention consists in using such substantially pure gases for fillingelectric glow lam s, as I have ascertained that when the remainder of nitrogen and other impurities is removed so far that they can no more be traced by the ordinary spectroscopic methods, the purified atmosphere of rare gases entirely changes the behavior of the carbon, its life aswell as the load-capacity of the filament being increased quite materially.

Icannotundertake at present to definitely state the reasons for this, but I believe that there are two circumstances cooperating with each other which were practically unknown up to date. On the one hand the natural vapor tension of carbon of any kind is apparently far lower than could be supposed accordlng to prior experiments. 11 the other hand I believe that although nitrogen is practically inert at somewhat, lower temperatures, its aflinity toward carbon is increased to an extraordinary extent as soon as a certain limit of temperature is exceeded. very small quantities of nitrogen then exert inga very obnoxiouscltect, the more so, as this effect does not enter into appearance by the tact that the small, quantities of nitrogen combine with the carbon, but by the fact,

that these combinations are permanently decomposedin other places, carbon being deposited at the same time, so that one and the same small quantity of nitrogen will then exert its obnoxious effect repeatedly.

()tcoursc, if to the purified rare gases other substances are admixed, such as for instance a certain quantity of mercury vasubstantially free of nitrogen.

2. An electric carbon filament glow lamp having its filament surrounded by pure argon substantially free of nitrogen.

3. In a glow lamp in combination a lamp globe, a carbon filament inclosed Within said globe and an atmosphere of pure rare gases substantially free of nitrogen surrounding 15 sald filament.

4. In a glow lamp in combination a lamp globe, a carbon filament inclosed within said globe and an atmosphere of pure argon substantially free of nitrogen surrounding said 20 filament.

In testimony whereof I affix my signature in presence of two witnesses.

HEINRICH BAUMHAUER Vitnesses Max J AnLoUsm, GERTRUI) KnAnsKowsKn 

